The capital Latin letter N is used in mathematics to represent the set of natural numbers. Usually, the letter is presented with a “double-struck” typeface to indicate that it is the set of natural numbers. Otherwise, N is also used as a variable.
Set of natural numbers.
The Latin letter n is commonly used in math as a variable.
The set of natural numbers, also called the counting numbers, contains the numbers 0, 1, 2, 3, ...